/Engine/Source/Editor/UnrealEd/Public/FileHelpers.h
Broadcasts the OnPrepareWorldsForExplicitSave event to allow validation and changes to worlds before they're saved. Used for Editor triggered explicit saves caused by user input such as ctrl+s, or clicking the save button. Changes to worlds include dirtying the world itself or affecting its ExternalActors through Adds/Removes/Edits.
static void PrepareWorldsForExplicitSave ( [TArray](API\Runtime\Core\Containers\TArray)< [UWorld](API\Runtime\Engine\Engine\UWorld) * > Worlds )